As is known, many pourable food products, such as fruit juice, UHT (ultra-high-temperature treated) milk, wine, tomato sauce, etc., are commercially available in sealed packages made of a packaging material that has previously been sterilised.
A typical example of this type of package is the parallelepiped-shaped package for liquid or pourable food products known as Tetra Brik Aseptic (registered trademark), which is made by folding and sealing laminated strip packaging material.
The packaging material has a multi-layer structure substantially comprising a base layer for stiffness and strength, which may comprise a layer of fibrous material, e.g. paper, or of mineral-filled polypropylene material, and a number of layers of heat-seal plastic material, e.g. polyethylene film, covering both sides of the base layer.
In the case of aseptic packages for long-storage products, such as UHT milk, the packaging material also comprises a layer of gas- and light-barrier material, e.g. aluminium foil or ethyl vinyl alcohol (EVOH), which is superimposed on a layer of heat-seal plastic material, and is in turn covered with another layer of heat-seal plastic material forming the inner face of the package eventually contacting the food product.
As is known, packages of this sort are produced on fully automatic packaging machines, on which a continuous tube is formed from the web-fed packaging material; the web of packaging material is sterilized on the packaging machine, e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution. Once sterilization is completed, the sterilization agent is removed from the surfaces of the packaging material, e.g. evaporated by heating. The web of packaging material sterilized in this manner is maintained in a closed, sterile environment, and is folded and sealed longitudinally to form a vertical tube.
The tube is filled with the sterilized or sterile-processed food product, and is sealed at equally spaced cross sections, along which it is eventually cut to form the packs. These pillow-shaped packs are then folded mechanically to form finished, e.g. substantially parallelepiped-shaped, packages.
Alternatively, the packaging material may be cut into blanks, which are formed into packages on forming spindles. These packages are filled with the food product and sealed. One example of this type of package is the so-called “gable-top” package known by the trade name Tetra Rex (registered trademark).
Once formed, the aforementioned packages may undergo further processing, such as applying a reclosable opening device to enable the product to be poured out.
At present, the most commonly marketed opening devices comprise a frame defining a pour opening and fitted about a pierceable or tear-off portion of a top wall of the package, and a cap hinged or screwed to the frame, which is removable to open the package; as an alternative, the use of different types of opening devices, such as slidingly operated opening devices, are also known.
The pierceable portion of the package may be defined e.g. by a so-called “prelaminated” hole, i.e. a hole formed in the base layer of the packaging material before coupling this layer with the layer of barrier material, which is therefore intact and closes the hole itself, thus ensuring hermetic sealing and asepsis although resulting easy to perforate.
In the case of aseptic packaging machines, the opening devices are normally fitted directly to the packages, after they are formed, in units placed on the production line downstream from the packaging machine.
The aforementioned units substantially comprise a gluing assembly within which a fastening portion of the opening devices is coated with a layer of adhesive, an application assembly within which the opening devices are applied on respective packages and a pressure assembly within which the opening devices are pressed on the respective packages for a time required to allow the cooling of the adhesive and the complete adhesion of each opening device on the corresponding package.
Application assemblies are known, e.g. from patent EP1813533, comprising a first linear conveyor adapted to feed a sequence of packages along a first rectilinear path, a second linear conveyor adapted to feed a sequence of opening devices along a second rectilinear path, and a rotating carousel conveyor comprising a plurality of gripping members and which is adapted to carry the opening devices from a withdrawal station to an application station of the opening devices on the respective packages.
Each gripping member is movably constrained to the carousel conveyor radially to a rotation axis of the carousel conveyor between a retracted position and an advanced position.
More specifically, each gripping member is placed at a maximum and at a minimum radial distance from the axis of the carousel conveyor respectively in the corresponding advanced and retracted position.
Each gripping member is arranged in the advanced position when it withdraws the opening device from the first conveyor, it is advanced in the retracted position by the carousel conveyor, and it is arranged in the advanced position when it applies the opening device onto the corresponding package.
Specifically, each gripping member applies the opening device on the corresponding package in a direction perpendicular to a top wall of the package and radial with respect to the axis of the carousel conveyor, so as to arrange the flat fastening area of the opening device parallel to and in contact with the top wall of the package itself.
Although reliable and effective, the disclosed application assemblies may further be improved.
Specifically, a need is felt within the sector to enhance the flexibility of the application assembly, under several points of view.
In particular, a need is felt to process differently shaped opening devices and/or to apply the adhesive substance along differently shaped patterns, without substantially re-configuring the gluing assembly and the application assembly.
A need is also felt to render the cycle-time of the gluing assembly as independent as possible of the cycle-time of the application assembly.
Furthermore, a need is felt to increase the throughput of the unit up to values of more than 40000 packages/hour.
Finally, a need is felt to reduce as far as possible the pitch between the package processed by the application assembly, without impairing the precision of the coating with the adhesive substance and/or of the application of the opening device to the package.